Human interferon (HuIFN-.alpha.) is known to be useful in the treatment of certain forms of tumors, e.g. hairy cell leukemia.
HuIFN-.alpha.has also been recognized for some time as a potentially valuable drug for the treatment of some virus infections (see e.g. The Biology of the Interferon System, Elsevier/North Holland Biomedical Press 323-380 (1981)). HuIFN-.alpha. has been reported for instance as being effective in the treatment of ocular Herpes Simplex, when applied at high dosages together with Trifluorothymidin (Sundmacher et al., Lancet II 687: (1978).
The compound 2,6-bis (diethanolamine)-4, 8-dipiperidino-pyrimido [5,4-d]pyrimidine, which has the generic name dipyridamole, and its preparations have been described in, for example, U.S. Pat. No. 3,031,450. Dipyridamole is a well known vasodilator and also has platelet aggregation inhibiting properties; in view of these properties it has found widespread use for many years in the treatment of chronic coronary insufficiency and in the prophylaxis and treatment of heart infarcts as well as in the prophylaxis of arterial thrombosis.
Antiviral activity for dipyridamole has been reported. For instance, in East German Patent No. 116,752 (C.A. 85; 37239r) compositions containing dipyridamole for the prophylactic and therapeutic treatment of virus diseases in humans and animals are described. In Acta Virol. (Engl. Ed.), 21(2):146-150 (1977), it is described that when tested in chick embryo, human diploid and FL cell cultures, dipyridamole inhibited D such as vaccinia and pseudorabies virus and those of the Chlamydial family and RNA viruses belonging to Picornaviridal, Togaviridal, Orthmyxoviridal and Paramyxoviridal but that Adenoviruses 1 and 3 were resistant to the compound. In a further publication (Acta Virol. [Engl. Ed.] 22(4):287-295 (1978)) various derivatives of dipyrid found to be active against a variety of virus such as Coxsaki BI virus, fowl plague virus, vaccinia and pseudorabies virus. The publication Z. Allg. Mikrobiol. 22(9):61-670 (1982), describes work carried out on the in vitro effect of dipyridamole on pseudorabies virus in which it is stated that the antiviral activity of dipyridamole may be due to blocking of the synthesis or the incorporation of infectious viral DNA into the virus core.
A number of authors have reported the induction of interferon using dipyridamole. Thus in Vopr. Virusol, 32(3):294-297 (1987), the use of dipyridamole as an agent for preventing acute respiratory viral disease was evaluated. Dipyridamole is described in this article as an interferon inducer. Also in Zh. Mikrobiol. Epidemiol. Immunobiol. (6):26-30 (1985), is described a report on the "epidemiological effectiveness of dipyridamole, an interferon-inducing agent used for the prevention of influenza and viral acute respiratory diseases." The report claims a pronounced epidemiological effectiveness of dipyridamole.
No authors have reported or suggested the combined uses of dipyridamole and IFN-.alpha. in the treatment of, or prophylaxis of, viral infections, or suggested that any worthwhile results could be expected from such a combined therapy.